text:
What is the relation between roll angle and pitch angle?
I was wondering about roll angle and pitch angle values.
Will I get same pitch angle at different roll angles and vice-versa?
For example. At its initial position, the aircraft is standing on the runway). I got roll and pitch values from a sensor. Lets say X and Y resp. Now, when aircraft is taking off, it is obvious that it will pitch up so  my pitch angle will change to lets say Y1. Now if I look for roll Value, will it be same 'X' or it will be different?

I am unclear what you are asking. For example, are you asking when a small aircraft performs a coordinated turn will the nose drop below the horizon, unless corrected for using pitch controls?

@DeltaLima: I was going to use diagrams from NASA - maybe they or something similar will be useful? Voted to reopen.

@DeltaLima May I know how to open it?? i have edited and added more explanation.. still it shows on hold

@RedGrittyBrick Exactly. I used something similar. This is about the order of application of euler angles; not about aviation specifically but it is definitely in scope.

@pratik: several (five I think) people have to vote to re-open a closed (i.e. on-hold) question before it gets reopened. You can flag it for moderator attention if this doesn't happen within (say) 24 hours.

If the answer will be pitch and roll are unrelated i will reopen this.

@DeltaLima I think question is now reopened... will you please post your answer?... thanks

Roll, pitch and yaw are rotations about the principle body axis of the aircraft. Roll angle, pitch angle and yaw angle together describe the attitude of an aircraft.
The principle body axes are:

X-axis is the longitudinal axis pointing out the nose of the aircraft. Rotation about the x-axis is called roll. Roll rate is denoted $p$, roll angle is denoted $\phi$
Y-axis is the lateral axis pointing out the right wing. Rotation about the Y-axis is called pitch. Pitch rate is denoted $q$, pitch angle is denoted $\theta$
Z-axis is the vertical axis pointing down. Rotation about the Z-axis is call yaw. Yaw rate is denoted $r$, yaw angle is denoted $\psi$

Initially when all angles are 0, the aircraft is wings level, nose pointing at the horizon and heading north.

The angles $\phi, \theta, \psi$ describe the attitude with respect to this initial positions. They are called Euler angles
The rotations are applied in backwards order, first yaw ($\psi$), then pitch ($\theta$) and finally roll ($\phi$).

This describes almost every possible attitude uniquely, unless the pitch angle is +/- 90 degrees. Then roll and yaw will become ambiguous.
Now back to your question. Initially on the runway the roll angle of the aircraft is 0 degrees. If the aircraft pitches up ($q$ becomes positive for a while), the roll angle will not change.
However, if initially the roll angle was non-zero, the roll angle will be affected by a pitch-up manoeuvre. You can easily visualise this with your hands.
Open your right hand with the palm facing up, you thumb at a right angle to the fingers. The middle finger is the X-axis, the thumb is the Y axis.
Now roll your hand 45 degrees counter clockwise, keeping the fingers pointed at the horizon. Your thumb will now point 45 degrees into the air. This was a pure roll manoeuvre, the pitch angle is still 0 degrees.
Now flap your hand 90 degrees up using your wrist, this is a pitch up manoeuvre since you rotate about your thumb axis which is the Y axis.
Now you see that your fingers are all in the same vertical plane, pointing 45 degrees up to your left. If you describe this position with respect to the initial position, the pitch angle is 45 degrees, and the roll angle is 90 degrees. So pitching 90 degrees resulted only in 45 degrees of pitch, but also in 45 degrees of extra roll.
Because the roll-angle was non-zero before we started to pitch, the pitch rotation affect the roll-angle.
If your sensor is not aligned with the body axes of the aircraft, you will see a lot of cross-effects between the angles during a take-off.
The mathematical relation is well described on this page, which is also the source of the images above.

The situation you describe while pointing nose 90 deg up, and roll and yaw becoming ambiguous, can be solved with quaternions.


text:
Would an A320 override the autothrottle due to an erroneous radio-altimeter?
The pilots of Turkish Airlines Flight 1951 had multiple issues with the auto-throttle setting itself to idle during approach: despite manually adding throttle, the plane stalled and crashed before reaching the runway, from a sequence of events initiated by the reaction of the auto-land system to one faulty transducer.
The fault was masked because:

The PF was the first officer, his radio altimeter was working correctly.
Autothrottle in the 737 only looked (looks?) at the captain's side.
The glide path was intercepted from above and throttle reduction was expected.

The F/O was an ex military pilot with 4000 flight hours receiving line training, when the stick shaker activated he immediately gave full throttle. The captain took over command, during which the autothrottle set back to idle again. The plane then stalled and re-applying full thrust was ineffective. Full investigation report pdf here.
The plane was a Boeing 737-800. Had it been an A320, would the autothrottle have reacted in the same way, and set the throttle to idle upon detecting zero radio altitude?

Yes the question is if the auto-throttle switches to flare mode (I assume this is the same as Retard in a B737) with only one radio altimeter detecting flare height. Indeed the DSB report mentions on page 66: The conclusion is that the captain should have made a go-around in accordance with Turkish Airlines’ standard operating procedures once the approach during the ILS approach had not been stabilised at 1000 feet. ...

...It also mentions on page 66: The captain bears the final responsibility for a safe flight and compliance with the statutory regulations and standard operating procedures as long as these do not conflict with the safety of the flight. It is likely that, in light of the research above, the captain did not see the continuation of the approach below 1000 feet as a contravention of the safety of the flight.

what's the point (and source) of the image?

Own photo, it shows the throttles, cockpit and working environment.

I know what it shows. I still don't see what does it add to the question.

These are the throttles that the question is about.

In AIRBUS, The «Flare mode» brings  automatically the thrust to idle provided the autothrust is under the dependance  of the FMGS, in this case irrespective of the pilot action moving back the levers or not, the thrust will go to idle. On the other hand if the approach is done in SPEED mode AND WITHOUT THE AUTOPILOT USED IN PARALLEL, it is mandatory to move manually the levers to idle, otherwise the autothrust will increase the power after landing just to maintain the approach selected speed, in this case it is important to move the levers to idle during flare.
Please refer to the following website:
https://forum.aerosoft.com/index.php?/topic/113217-need-help-with-manual-landing-a320/#comment-762234
You will read:

Remember that "RETARD" is a reminder, not an order: however, with the A/THR engaged in a manual landing if you do not retard the thrust levers to idle the system will add thrust to keep the the aircraft on target speed, which will result in you continuing to fly gently a couple of feet above the runway! In an autoland the system will automatically reduce the thrust to idle

Similarly, please refer to:
https://www.skybrary.aero/index.php/Autoland
You may read:

The pilots must program the FMS (or tune the appropriate radio aids), configure the aircraft for landing and engage the autopilot and autothrust systems in the normal fashion. The Autoland system then provide inputs to the aircraft flight controls and adjusts the engine power settings in order to maintain the required approach profile and land the aircraft safely without pilot intervention. Some systems require the pilot to reduce thrust to idle when performing autoland. The Airbus requires the pilot to move the thrust levers to the idle positon when the autocallout calls "RETARD" at 10' RA. HOWEVER, the autothrust has already reduced the thrust to idle before this point - the retard call is to remind the pilot to match the thrust levers to the demanded thrust requirement. In all cases, the pilot must select reverse thrust settings. The autopilots will be disengaged after landing to taxi clear of the runway

As a summary if on approach the AP/FD is in approach mode, the autothrust
is in thrust mode and automatic idle occurs even if the pilot doesn’t move the lever to idle. On the other hand if the autopilot is not used, and the autothrust is in « speed mode », manual reduction to idle is necessary.
In all cases, at landing the « retard » aural annunciation is done.
Important note: on Airbus, a single radio altimeter failure will change the autothrust redundancy, at worst case an automatic disconnection will not prevent to reengage the autothrust, this will not prevent correct functioning of the autothrust, that is the idle is automatic if the autothrust is coupled to the autopilot; the idle should be manually forced if the autothrust is in SPEED mode and is not coupled to the autopilot.
Anyway bringing back the levers to idle is mandatory if reversers will be used
Thank you for ymb1 about RA. RAs are not voted

Your answer appears to directly contradict the FCOM citation in the accepted answer. Can you justify your statement?

I added more details, thank you

The citation concerns the case «  autothrust »is used without autopilot,  when autothrust is used with autopilot the thrust reduction to idle is automatic irrespective of the levers position.

@user 71659, please read my updates. Kind Regards

Thank you. May be it is not a voting, but switching, on the simulator when RA1 is faulty and autothrust1 active ( even though it doesn’t show as being N°1) the autothrust will disconnect, but may be reconnected, which means that autothrust2  will take over, without knowing that it is N°2. On AIRBUS  the display 1 or 2  does not show for the autothrust, because they are selected by the same button and the automatic choice is transparent.. However with autothrust1 being active and RA2 failing, no disconnection will occur. What is important is that reconnection will be possible when one RA fails.

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text:
What happened to EC-ATQ?
EC-ATQ was a Douglas DC-7C.
It was damaged beyond repair on 2.10.1970 in Madrid.
Does anyone have more information?
Was a piano dropped on top of it and nobody was willing to take the blame?

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text:
What can a pilot do if an air traffic controller is incapacitated?
I watched this video:

where a Las Vegas controller is on duty alone and suffers a stroke.
The pilots become quite uncomfortable with the situation and basically everything is stopped.
Someone finally calls the company and gets them to check up on the controller.
Fortunately it was not that busy, and no other emergency emerged.
What else could the pilots have done to remedy the situation?

I thought controllers (as pilots) didn't work alone (to ensure redundancy)

@ManuH Well in this case obviously nobody was there to help her or notice that anything was off. One pilot even asked for her supervisor, but was struck with silence.

That's scary. I felt so sorry for the controller. Hope she got well.

@Manu H: Many, perhaps most, private pilots fly alone.  And low-traffic towers can be staffed by a single controller, partularly during off-hours.  Though I'm very surprised that Las Vegas would be in this category.

@ManuH sometimes during quiet hours there are only 2 people in the tower. One of them goes to the toilet or gets to grab some coffee, leaves the other alone for a few minutes. That's what caused a midair over Germany...

What can they do? CPR, I suppose. If they're in the tower.

@PeterA.Schneider CPR does no good in case of strokes.

True, in most cases (unless the stroke leads to breathing or heart problems). But I tried to answer the general question inspired by the specific example.

@jamesqf I should have precise I was thinking about airliners pilots

In theory, if the lone tower controller is incapacitated, the airport is no longer controlled and pilots should use the standard procedures for uncontrolled airports, i.e. making traffic calls on CTAF.
In the KLAS case, the pilots had every reason to expect the tower to be open, and rather than getting no response, they were getting unintelligible gibberish. As a result, their reactions varied.
If the situation had persisted, one of them would have notified Las Vegas Approach, who in turn would have started advising pilots of the uncontrolled field ("change to advisory" rather than "contact tower"), and everything would have proceeded fairly normally. Since it happened at night, traffic volumes were low enough that CTAF would have worked okay, which is probably why only one controller was on duty in the first place.
However, a supervisor was in the tower on break at the time, just not in the cab, so he was able to take over relatively quickly and resume normal operations before that actually happened.

There's not much else they can do in a situation like this. ATC, in this case the tower controller is the only person(instance) that has a comprehensive enough view (both literally and metaphorically) of the situation to give orders, clearances etc.
What the pilots can and will do in a case like this, is proceed according to their last clearance. If you are cleared to land, you land. If you were cleared to taxi somewhere, you taxi untill you reach the clearance limit (typically a holding point, gate, or place at apron) and so on.
When you reach the clearance limit, if you want to proceed you ask for further advice/clearance. After landing you would vacate the runway, then ask for taxi instructions (if none were automatically given). If you were taxiing for takeoff, and reach, say, a holdingpoint, you'd tell ATC you are ready for takeoff at that holdingpoint. If you are on approach, but not cleared for landing, you obviously have no other option but to conduct a missed aproach as per published procedure.
When you reach your clearance limit and you don't hear anything from ATC, or as in the video, the communication is incomprehensible, you simply stop and wait (or go around) and keep trying to communicate with ATC. And as in the video, if this situation persists, you try establish communications with someone else who can check the status of the ATC.
One should keep in mind that despite having an ATC control your movements, as a pilot you still have to maintain an alert lookout. You allways have to be aware of what is happening around you, by looking out, listening to radio communications etc. Someone might have misheard/-understood their clearance or act unexpectedly for any other reason, and you have to be "awake" and ready to adjust your actions.
*Edit: I'll take the liberty to add some hindsight here. From the very beginning of the recording it is dead obvious there is something wrong with the controller. Even without seeing her, it's pretty clear she's either under the influence, or having a stroke, latter of which she was. It's kind of disturbing that none of the flightcrews either recognized this, or if they did, decided to let it go (at least one obviously did notice the gibberishly speech and made a remark about comedy or something). It's also weird that the controller kept on working throughout the stroke, but I'm guessing the stroke had impaired her judgement.
So: if you ever encounter someone speaking like that, check out what it's about. You might end up saving that someone's life.*

I was wondering about why the pilots took so long to send someone there. The probably all had cell phone coverage. I guess it's because ATC usually gives commands, and one does not question the authorities.

@Christian Almost any pilot has access to multiple radios, often configurable in a dual-receive configuration. Unaugmented, cellphones have problems at altitude and high speed. The pilots have easy access to the frequencies for Approach (or the corresponding service in other areas); they either just spoke to them or expect to speak to them soon. (ATC giving the frequency during handover serves more as a sanity check.) It would be more reasonable for the pilot handling the radios to just switch frequencies and keep monitoring Tower for a minute to alert e.g. Approach than to use a cellphone.

Is approach reachable from the ground? If I understand the situation correct most planes have been on the ground, waiting for clearance to depart.

@Christian As for "one does not question the authorities", it is well within the purview of a pilot to reject a clearance and ask for a different one, if they feel the clearance they received would somehow be unsafe. If ATC tells a pilot "climb and maintain (FL) 430", but the pilot knows that their airplane at its current weight can only maintain up to 390, they are well within their rights to say something like "unable, require 390 or below due to weight". The controller will then issue a different one; maybe "left turn to 220 for separation, climb and maintain 370, expect turn to 240".

@aCVn I meant it more like a psychologial issue, not a merit of the law. And most of the time the pilot does, what ATC tells them to.

@Christian I haven't watched the video, but as a pilot you certainly can relay through another aircraft if necessary. So if Delta 9876 can't raise Springfield Approach on their own, a next step might be to switch to an appropriate frequency, listen for an appropriate flight, and transmit something like "Southwest 123, Delta 9876, are you able to relay to Springfield Approach?". Indeed if you're on the ground and not moving, then a cell phone might also be a reasonable alternative, assuming you have the phone number for Approach!

If the controller sounded like the one on the video, 911 would be a viable option when dialing. There are actually some psycological reasons why nobody called 911 in this case, but they would be a subject of a whole new question...

@Christian Yes! It's the "single point failure" problem, authority version. You reminded me of this tragic situation: https://www.hbo.com/documentaries/theres-something-wrong-with-aunt-diane/synopsis My takeaway: two parents are better than one not for "moral" reasons but because they can check each other when things go wrong. Also: don't travel separately if at all possible.

There was a case in DCA (Reagan National, near Washington, DC) of the lone controller at night falling asleep.  In that case Washington Approach declared the airport uncontrolled and took over the tower frequencies.  At least one flight landed without receiving clearance from the (asleep) controller.

https://www.ainonline.com/aviation-news/air-transport/2011-03-24/controller-reagan-national-fell-asleep-duty


text:
Why did the Avro Vulcan use a delta wing?
Why did the Avro Vulcan use a delta wing?
The B52, from the same era, used a swept wing, and had a higher maximum speed.
In the answer to What are the advantages and disadvantages of a delta wing compared to a swept wing?, Peter Kämpf explains that a swept wing is ideal for subsonic airliners.
No one else has built a subsonic delta-wing aircraft since, military or civilian. Why did the designers of the Vulcan make this unusual choice for a subsonic aircraft?

By Ministry of Defence [OGL 3], via Wikimedia Commons

Because it's one of the coolest shapes to ever fly.

"Because it's one of the coolest shapes to ever fly" - and AFAIK nobody ever did a barrel roll in a B-52. The second Vulcan off the production line did one at its first Farnborough airshow in 1955. https://www.youtube.com/watch?v=GPuTgcrA2Zs

@alephzero In 1955, Tex Johnston did a barrel roll in a Boeing 707. It didn't fit the image his bosses wanted to project, however.

@DavidK: No, but it did net Boeing a lot of orders for the 707.  Which was Johnston's intention - when his superiors asked him what he thought he was doing, he famously replied "Selling airplanes".  And it worked.

For a smaller radar cross-section, obviously.

I would not say that no other bomber ever had delta wings. Convair B-58 Hustler and Mirage IV both have delta wings. They are both supersonic though.
The B-52 did not have to worry too much about MTOW and empty weight since SAC already had bases with long runways capable of really heavy aircraft. That's thanks to B-52's predecessor B-36. The B-36 was the heaviest land based aircraft of its time and ground pressure was a very real concern when basing that beast. Britain did not have such bases. The Vulcans predecessor, the Avro Lincoln, could take of from grass fields.

Thank-you!  Google Books links are too lengthy to put here but The Avro Vulcan: A History puts take-off speed at 130 kt, and A Century of Air Warfare With Nine (IX) Squadron, RAF puts runway requirement at 5,000 ft.   For the B-47, I found landing speeds of 180 kt and runway length (without chute) of 11,000 feet.   As I understand it, delta wings allow for higher angles of attack thus accounting for the lower speeds.  And you've explained the difference in requirements between the RAF and the USAF.   Makes sense to me!

The Vulcan was capable of supersonic flight.  The B52 never was designed for that.  The Vulcan shows heavy influence of 1940s high speed designs (The Me 163 Komet), but as can clearly be seen by the MTOW chart, suffers from delta blues as far as lifting capacity and range. Deltas simply cannot lift as much as conventional wings.
They did, however, provide an easier path, particularly in those times, to supersonic flight.  By generating lift with vortex flow, a thin, flat wing can be employed, side stepping Mach airflow compression issues (rocket fins routinely go supersonic).  Deltas enjoy a wide flight speed envelope and are found in applications from hang gliders to many supersonic aircraft.  They are very strong and easy to make.
However, we do not see them in subsonic transport or bombers because they are not as efficient in generating lift for their drag.  Blended wing/body, same thing.  For long range efficiency, the wing itself does its job, everything else belongs in a streamlined tube.

"The Vulcan was capable of supersonic flight" do you have any sources for this? Beyond the one instance of overspeed, which may or may not have led to brief supersonic flight, the Vulcan was not designed for it. A further clue is that there were subsequent proposals to develop a supersonic Vulcan (Avro Type 732), meaning the team was aware of the limitations of the existing platform.

From wikipedia: "A cruising speed of 500 knots (580 mph; 930 km/h) at heights between 35,000 ft (11,000 m) and 50,000 ft (15,000 m) was specified." and  "Maximum speed Mach .95 indicated" but please point out the correct paragraph if I´m missing something. On the contrary, your source states "The Avro 732 was a 1956 proposal for a supersonic development of the Vulcan [...]"

I will try, for now (I'm at work) the F 86 Sabre Jet was also built to be high subsonic, but could go supersonic in a dive.  This was a handy trick, as other early jets could not do this.  Legend has it a Sabre broke the sound barrier the same day as it was done, under controlled (and much safer) conditions by the X-1.  The boom, from a dive, was much louder.  As mentioned, rockets routinely were already breaking Mach 1.  The Vulcan, with its hugely stable delta, could as well (without an all moving elevator or MCAS).

The Vulcan was also difficult to see on radar.  This may have been the primary driving force in its planform.  But I would not doubt it's designers dreamed of supersonic flight as well.

Vulcan was built to a specification which gave it a top speed capable of outrunning the fighters of that time. The specs from wiki make it too slow to do that. The Mk 10 used the same engines adopted much later for the Concord. Rumour had it that the last ships off the line were capable of 900mph. In the fifties six Vulcans did an exersize. They flew over the pole and attacked six major US cities. They were not intercepted. After the initial report in the newspapers a D notice made sure that the incident was hushed up. It did appear as a front page feature in the AVRO news, A monthly company newsletter.
Much later the Valkerie was developed in the US. This compensated the nose dive tendency by adding a canard wing on the nose.Later again the B1 was a similar shape. The latest idea is now the blended wing design which like the Vulcan is capable of carrying 50% more than an aircraft with a fuselage. Just in case you missed the point. The initial research was done in the AVRO factory in Chadderton. Tests in a huge tank found the wings suffered fatigue and  fell off. The solution was found when it was suggested that a line of perforations along the breakage line would solve the problem. The toilet paper never ripped along the perforations. Solution Honeycomb sections. Saved lots of weight and was far stronger.

That toilet paper may not rip along the perforations has nothing to do with the perforations themselves, but with the fact that any paper rips easier fiber-wise. Because of production reasons, a roll of toilet paper has the fiber direction 'wrong'...

also, would you mind providing sources for your statements?

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text:
Is there any Class G airspace south of Portage Bay in Seattle?
I would like to apply for a waiver to fly a UAS to take pictures over the campus at Seattle Pacific University that is located just south of Portage Bay in Seattle but I'm told that can only be done in Class G airspace.  Is there any Class G airspace in that area?  Thanks.
Alan Rither

Is this the location you are asking about? If so, SPU is located under Class G airspace up to 1200 AGL. However, it is close to the Kenmore seaplane base. You reference waiver. Would this be under §107?

As a pilot who flies for Kenmore Air, I appreciate your professional attitude toward flying your UAS.  Please be aware that the location you've described is exactly within the departure corridor for seaplane traffic out of Lake Union (W55).  Kenmore Air alone has 50+ outbound flights/day through there, 8 am - sunset, climbing, between 500 and 800'.  Add to that multiple scenic flights by Seattle Seaplanes, other float traffic from Renton (W36) and Kenmore (S60), helicopter training, banner towing, Coast Guard and TV helos... This is an EXTREMELY busy low-altitude air corridor!

I don't know the regs regarding your intended UAS flights, but if a waiver isn't required please contact me directly and I'll help put you in contact with the commercial firms that utilize that corridor, so as to advertise your intentions as widely as possible and thus minimize conflct in that flight corridor.

How could I forget: SPU is under the flight path for King County International Airport (KBFI), one of the nation's busiest non-hub airports.  I hope my comments here have impressed upon you the density of low-altitude commercial and GA traffic precisely where you intend to operate!  For everyone's sake (particularly my ass!) please use care and diligence!!!

And because what you're proposing personally terrifies me as a commercial pilot operating there daily, I urge you to become better aware of the geography annd points of reference within which you intend to operate.  For example, SPU is NOT "...located just south of Portage Bay...".  SPU is located just south of the Fremont Cut, which is a sect

Oops, fat fingers.. section of the Ship Canal.  Portage Bay is a body of water several miles to the east.  The University of Washington is on the north side of Portage Bay.  Are you sure you know where you intend to operare???

The larger question here may depend on what kind of photography operation you are doing. If you are taking the pictures for someone else, you will probably need to be a licensed sUAS pilot under §107. If you are flying and photographing exclusively for recreational purposes, you probably don't need to be licensed. In either case you shouldn't need a waiver for low altitude flights over SPU, but you may need to notify the nearby seaplane base. For more information about drone flying see KnowBeforeUFly.

It appears that Seattle Pacific University is located 14NM north of the SEA VOR on the 350° radial.  This puts the university under class B airspace.
Over the university, class G airspace starts at the surface and extends upwards to 700 FT AGL, class E airspace extends from 700 FT AGL up to 3,000 FT MSL and class B airspace extends from 3,000 FT MSL to 10,000 FT MSL.
From a regulatory standpoint the FAA has a set of guidelines that are found in 14 CFR Part 107.
There are rules stating you cannot fly an UAS over persons who aren't part of the flight or with the traffic area of airports.  You also cannot operate in areas where class B, C, D or E extends to the ground but that appears not to be the case here.

That area is class G up to 700 feet AGL. As has been pointed out in other answers, if you're doing the flight for any type of compensation you will need a part 107 uas license. Keep in mind that the FAA has a very broad definition of "compensation."
If you are doing this as a hobby then you can fly under hobby rules. There are no waivers under hobby rules. The FAA has been given pretty much a hands-off order by Congress for hobby flight. The regulations they set out are really vague. They refer the rulemaking to non-government entities such as the Academy for Model Aeronautics and ask you to follow their guidelines. Generally if you fly under 400 feet and use common sense (don't fly over people, etc) then you're legal. The only thing that the FAA requires of you under hobby rules, outside of controlled airspace, is that you contact any airport within 5 miles. Here's the catch: there are 13 different airports and heliports within 5 miles of the campus.
If you're operating under hobby rules then you need to find out if the city, county or state has any regulations on drones. This is a very sticky subject in aviation right now, as you can see from user45726's reaction. Pilots are understandably concerned about colliding with drones. I don't live in Seattle, but it seems hard to imagine that planes would have a good reason to be flying less than 500 feet over the campus. Out over the water there, that's a different story, with all the seaplane bases nearby.
That said, there's a lot of aviation activity in that area, so an excess of caution is called for.


text:
Does a 100 Hour Inspection Start Over Every Annual?
If an airplane receives a 100 hour at 350 hours and has an annual at 400 hours, does the next 100 hour inspection need to take place at 450 hours or 500 hours?

Are you asking about FAA regulations?

The annual will reset the 100 hours.
See 91.409

(b) Except as provided in paragraph (c) of this section, no person may operate an aircraft carrying any person (other than a crewmember) for hire, and no person may give flight instruction for hire in an aircraft which that person provides, unless within the preceding 100 hours of time in service the aircraft has received an annual or 100-hour inspection and been approved for return to service in accordance with part 43 of this chapter or has received an inspection for the issuance of an airworthiness certificate in accordance with part 21 of this chapter. The 100-hour limitation may be exceeded by not more than 10 hours while en route to reach a place where the inspection can be done. The excess time used to reach a place where the inspection can be done must be included in computing the next 100 hours of time in service.

It is also worth nothing that the requirements (14 CFR 43 Appendix D) for an Annual inspection include those requirements for a 100 hr inspection.


text:
Why do Airbus and Boeing have different approaches to bleed air systems?
Reading Wikipedia and other questions like this, made me curious as to why Boeing uses bleedless architecture for its B787, while Airbus thinks differently for its A350 XWB (and Rolls-Royce thinks the same).
Both companies switched to composite materials for their new aircraft so they agree about some new technologies, but not all, since they have different approaches to the air systems.
Why did Airbus remain more conservative on this topic (even if its model is about 5-7 years younger than the B787)? What is Airbus's argument to sustain this choice and how does it compensate the disadvantages (cited by Boeing in linked post) of the traditional bleed air systems?
To be more precise, development of new technologies bring both companies to share many new common approaches because advantages are clearly evident, for example: glass cockpit, composite materials, wing extremities (sharklets/raked wingtip/winglets), bigger fans, but they are different ideas about others, such as control yoke, flight envelope, chevron onto engines and, effectively, bleed air.
I found information about "why" Airbus choices to avoid chevrons or prefer a side-stick joystick for example, but not about bleed air systems

Why would you expect that a structural technology adoption would be indicative of a change in philosophy for the cabin conditioning and pneumatic systems? The composites part of this question is a red herring and it would be best left out, imho.

Both Boeing and Airbus believe that it is a good idea to make airplanes. Given this, how can they possibly disagree on anything? Oh, wait.

@DavidRicherby Thank you.

As a sidenote, the A350 and 787 composite fuselages very are different, so they did not "agree" in this respect either. The A350 uses composite panels on metal/composite frames, similar to traditional metal fuselages, whereas the 787 uses a one piece composite barrel.

I edit my question, considering your observations, to be more precise

Nobody can tell you for sure without insider knowledge, and insider knowledge would be confidential in this case, but ultimately it boils down to risk management. Every new development carries a risk of budget and deadline overruns and of problems surfacing in operation and the manufacturer needs to be reasonably certain they can put the product to market before they run out of money.
When Boeing started developing 787, the 777 was selling well, so they had the budget reserve to risk more innovation. And it did have some problems in operation with battery fires. Airbus was in worse position when developing A350, so they stuck to more tried technologies to keep the risk lower.

It's a possible explanation at which I did not think... thank you


text:
Accounting for torsional forces during wing load tests
According to this aviation.se question, wing load tests are done by placing weights on the wings (upside down).

This unfortunately only tests the wings bending loads (for cantilever wings) and the wing struts (for semi cantilevers) but not the torsional strength of the wings.
How do I load test a wing such that its torsional capacity is also tested?

You would have to calculate the torsional loads for a critical torsional loading case such as full aileron application at limit load, and distribute the sand bags chordwise to produce the calculated spiral loading.
That's quite an analytical task and is rarely done when the skin thickness/stiffness required for good aerodynamic qualities and flutter resistance is usually quite a bit more than the minimum required for adequate torsional stiffness to resist flight loads. So it kind of takes care of itself anyway and can be covered by analysis with suitable fudge factors, like most of the other load cases on the airframe.

For a static weight test like that, you can clamp a beam to the wingtip so that it sticks out perpendicular to the wing, then hang a weight from the beam tip. The longer the beam, the larger the proportion of torque/weight.

This would load the wing in almost pure torsion, however, so the results would not be conservative due to the possible torsion-bending couplings.


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Why did the F-104 Starfighter have a T-tail?
The F-104 Starfighter was launched in 1954, nine years after WWII. It had short stubby wings and a T-tail. According to wiki, the short stubby wings caused inertia coupling and the T-tail reduced this.
My question is: is that really the reason why the F-104 had a T-tail? How does that help reduce inertia coupling?

EDIT
@aeroalias answer has many of the reasons for the T-tail. Had edited the question with some additional info, it was suggested to put this in an answer instead.

@mins thx for that. The document mentions Since you do not need the maximum roll capability that the Starfighter has with full aileron deflection, the ailerons have been limited so that ample but not extreme rates of roll are available. The second preventive was the ventral fin with its increase in directional stability, especially at the higher Mach. No mention of the T-tail!

Given the era, the fact that it looks great might have played a part in the decision :) But seriously, a T-tail design is usually selected to give cleaner air flow over the elevator when (it is suspected that) the air flow coming off of the trailing edge of the wing is rather turbulent.

@jwenting I agree to both things: a) looks great (but I'm Italian and therefore biased) b) Considering the Starfighter had a Boundary Layer Control System that, I presume, generated quite a lot turbulence behind the wings, the T-tail was probably the best choice.

It could be because of the placement of the engine, the exhaust is dead in the middle, it was more difficult to make a conventional tail?

@aeroalias answer contains a link to the F-104 test pilots notes, which explains:

why the Starfighter has a T-tail;
what measures were taken to prevent inertial coupling from happening.

According to the document, the T-tail provided better stability, control, and trim characteristics throughout the speed range. It also provided the same aerodynamic coupling effect as wing dihedral does, that's why the wings have anhedral.
Inertial coupling is not an aerodynamic phenomenon. It has occurred in one of the first satellites put into orbit, which was longer than it was wide, and over time started to wobble around the axis of rotation, a phenomenon called nutation. Airplanes with a long wing span can maintain a high roll rate without pitch and yaw being affected - the Starfighter was the first plane with short wings, and with a high roll rate came nutation, with undesirable pitch and yaw effects. And also a challenge when turning, judging from the famous phrase of a Canadian pilot: "Banking with intent to turn."
The T-tail is not really a solution to inertial coupling, only a longer wing span around the CoG is. Inertial coupling was prevented by limiting the roll rate. The T-tail did increase directional stability of the vertical tail due to the winglet effect, as did the ventral fins.
So contrary to the wikipedia statement, the T-tail was not primarily implemented to reduce inertial coupling.

Inertial coupling is caused by a slanted axis of inertia with respect to the direction of flight. Shifting the horizontal tail up only increases this slant. Stubby wings have litte roll damping but do not cause inertial coupling. Also, the dihedral effect was more than enough and limiting it caused pronounced anhedral. It should be obvious that you are correct and the T-tail was only chosen for better effectiveness of the whole tail arrangement, mainly caused by the endplate effect and the backward shift of the horizontal tail on a swept vertical. You should accept your answer.

The initial preliminary designs had the horizontal tail in multiple locations (including in-line with the wing and cruciform), before settling on the T-tail by December 1952. The reason for selecting the T-Tail is given by Glenn L. "Snake" Reaves, Lockheed Production Flight Test Pilot in the F-104 Test Pilot notebook as

The high tail position was selected ... after extensive wind tunnel tests (which) proved that the location was necessary to obtain optimum stability and control about the pitch axis throughout the wide Mach range. The position also results in minimum transonic trim changes while accelerating to supersonic.

Another advantage was that the high tail on the swept vertical fin reduced interference drag. While the problem was inertial coupling was quite well known during 1950's, the design of the F-104 was frozen during the same period, so it is difficult to tell conclusively if that is the reason for F-104 having a T-tail.
The test pilot notebook also has some explanation about how the T-tail reduces the problem of inertial coupling:

If we now consider two facts about these rolling maneuvers, it will become clear how inertial coupling builds up:

The sideslip build-up is controlled by the induced rolling moment.

As sideslip builds up, the centrifugal or rolling forces increase and this tends to displace the aircraft fuselage perpendicular to the flight path.

The T-tail controls the the sideslip build-up by inducing a rolling moment. From the same document:

... the high tail position of the horizontal stabilizer raised the center of pressure.

Image from F-104 Test Pilot notebook

... whenever we sideslip an aircraft, a rolling moment is induced that resists the sideslip. This induced rolling moment is generally termed dihedral effect.
... with any sideslip, the restoring force acting through the center of pressure does not act through the c.g of the aircraft. Therefore, a sideslip condition actuates the restoring force on the tail but at the same time, induces a roll. ... now that we have raised the tail and consequently the center of pressure and the positive dihedral effect has been increased considerably.

The T-tail reduced inertial coupling by preventing sideslip buildup.

The last quote talks about dihedral effect, but the F-104 had a slight anhedral

That clarifies much, but there is a lingering question. Inertia coupling takes place in space as well, with satelites that were longer than wide and started to wobble around their axis of rotation. As I understand the notes in your answer, the T-tail provides a dihedral effect which would reduce roll rate, which is what would be required. It also raises centre of pressure so that sideslip stability is increased.

@TomMcW the wings had a slight anhedral. This was the result of the high dihedral effect due to the tail.


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What are the effects of a rejected takeoff?
When a pilot is abandoning a take-off, what are the effects on the aircraft performance? Can a pilot vacate the runway normally or is extra time on the runway needed? Is immediate assistance provided by the airport?

If an airplane is close to V1, the brakes - which have to absorb kinetic energy and dissipate heat - can get hot to the point where the tires automatically deflate, to prevent them from exploding. For a 747 this involves a lot of smoke and glowing brake disks.

Normally, though, (aborted takeoffs happen reasonably frequently wiithout disastrous results) the plane just needs to clear the runway have the brakes quickly inspected, wait a bit for them to cool down, and possibly top up fuel before attempting the next takeoff.

Note that the linked video was not a typical RTO, but was rather a test performed under worst-case conditions for certification purposes, including the use of completely worn brakes, a very high cut speed (200 mph!) and an aircraft loaded to MTOW. Also, this test may go quite a bit worse on an A340...

Glowing hot brake discs in the vicinity of tens of tons of kersone combined with a risk of explosing.  Sounds like somebody will also inform the firefighting department.

The outcome depends on the speed, aircraft, weight, and other factors.
If the takeoff is aborted at low speed (maybe up to 30-40kts), there may be no issues. The pilot would be able to vacate the runway and taxi back down to the end (assuming whatever caused the aborted takeoff is resolved).
Weights closer to the maximum takeoff weight or speeds closer to the maximum rejection speed (V1) would be major factors in making the situation more complicated. Both dramatically increase the amount of kinetic energy the aircraft must dissipate to slow down. At higher speeds, spoilers on the wings and thrust reversers on the engines can help. The rest is up to the brakes.
Some aircraft have brake temperature sensors that provide information to the pilots. They would not be able to take off again until the brakes cool down past a certain point, to ensure that if the aircraft has to abort the takeoff (again) they could safely stop the aircraft. Other aircraft may have a certain amount of time the pilots must wait. They should be able to taxi off the runway for this. The pilots may request assistance from fire crews to make sure there is no fire or to help cool the brakes. Some aircraft also have brake cooling fans.
If the wheel temperature exceeds a critical value, special fuse plugs will blow, allowing the tires to deflate. This prevents the tires from blowing out, which could cause damage or injuries. If the tires lock up during heavy braking, this can also cause the tires to blow out. If too many tires are blown or deflated, or the pilots otherwise feel they can't safely vacate, the aircraft could be disabled on the runway. The pilots would inform ATC, who would coordinate the assistance. If ATC notices smoke or flames, they will inform the pilots and may call for assistance as well. The fire crews will put out any fires and cool the brakes, and later the aircraft will have to be moved off the runway.
In order to be certified, aircraft must demonstrate that it can safely stop in "worst-case" conditions. This means that the thrust reversers are not used and the brakes are also at the most worn condition allowed. This puts the maximum amount of energy into the brakes while they are the least equipped to handle it. The tires may deflate but there cannot be any fire for 5 minutes to allow time for the fire trucks to arrive.

V-1 is not, strictly-speaking, the maximum rejection speed.  It is the maximum rejection speed for the specific case of a single engine failure during takeoff with no other damage resulting.  There are plenty of failures that would require rejecting a takeoff even after V-1 (for instance, an elevator failure or two engines failing simultaneously).

Depends upon the reasons for aborting the takeoff, how fast the aircraft is moving relative to V1, the amount of runway available to the aircraft, the response time of the flight crew to intervene and abort the takeoff, power settings used, etc.
Usually as part of the preflight process the crew will compute both the accelerate-stop and accelerate-go distances and brief them during the pre takeoff brief.  An accelerate-stop distance is the distance required to accelerate the aircraft at takeoff power from a standaing start to V1, thence abort the takeoff and stop the aircraft using braking.  Accelerate-go distance is the distance to accelerate the aircraft at takeoff power, continue to Vr, liftoff, and have a obstacle clearance of at least 35 feet at takeoff safety speed V2 if an engine failure occurs at V1.  Provided the airport does not have a nonstandard obstacle clearance departure ie no obstacles in the departure path requiring steep climb gradients the crew will compute accelerate-stop distance and verify that there is enough runway available for this.
As to whether to abandon the aircraft on the runway or taxi off, depends on the nature of the emergency.  Aircraft or engine fires or structural failures may require the crew to immediately abandon the aircraft once stopped on the runway.  System malfunctions which don’t pose an immediate danger but require termination of flight operations ie. malfunctioning vacuum or pitot-static systems, etc. will permit an aircraft to taxi back to a parking ramp for shutdown and maintenance.


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Is there a specific relation between sideslip angle and yaw rate OR how sideslip angle depend on yaw rate?
Since, yaw rate is controlled via rudder and sideslip angle can also be controlled by rudder, I want to know if there is any dependence of sideslip angle on yaw rate in fly by wire aircraft as I am working on the SAS design of a/c lateral/directional dynamics?

one is a rate and the other is an angle. are you asking about the relationship of a velocity w.r.t. a distance?

Hii...I am asking the relation in terms of direction ( +ve  or -ve). i.e. how  does positive/negative yaw rate relate to +ve/-ve sideslip angle?

Your question seems to be unclear with respect to its purpose. It might help if we knew what you are trying to find out. Can you describe your question a different way? I am assuming that you know what a sideslip is normally used to accomplish.

Since, yaw rate is controlled via rudder

No, yaw is controller by many things, and rudder is there mainly to compensate for them to keep the plane flying nose-forward.
The usual way to make a control system is that you control (with a PID controller):

Move elevator to target vertical (plane coordinates) acceleration.
Move ailerons to target roll rate.
Move rudder to target zero lateral (plane coordinates) acceleration. Lateral acceleration is measured by the ball in traditional cockpit.

Note that each axis is basically independent and rudder is only used to eliminate side-slip, which is proportional to the lateral acceleration unless you have asymmetric thrust or drag—and I have not heard of a FBW that would automatically correct for those conditions.
When flying with auto-pilot, the auto-pilot sets vertical speed target from altitude error and vertical acceleration from vertical speed error for the pitch and it sets roll from heading error and roll rate from roll error for roll axis. Autopilots don't set lateral acceleation targets at all—that is always zero.
That is why auto-land has much lower cross-wind limit—autopilot does not handle rudder, so it can't de-crab.

Sideslip angle β is the "sideways" angle of attack of the aircraft body. In a given time span, sideslip angle is the integrated signal of yaw rate, which is the integrated signal of yaw acceleration, which follows from the yawing moment and the inertia. This is the case in any aircraft, fly-by-wire or conventional control.
$r_{dot}$ = $M_β$ / $I_Z$
r = $∫$ $r_{dot}$ dt
$β$ = $∫$ r dt
Sideslip is an aerodynamic entity defined relative to air velocity (body axes), while inertial entities are defined in earth axes. A transformation matrix describes the relationship of the two axes systems. For flight behaviour the body axes form the frame of reference: a sudden side wind changes initial side slip angle at the start of our time interval, plus the moments acting upon the aircraft.

This answer is only correct under specific conditions (e.g. no wind) which you might want to spell out. As it is it is rather incomplete.

Meaning - Newton's law is incomplete?

@koyovis Sideslip angle can change by windshear with no change in yaw when viewed from an earth frame of reference (which is where sideslip is most useful).

Ah now I see what Peter means :)

No, there is no specific or dependent relationship between sideslip angle and yaw rate.
A momentary yaw rate can result in a slip, but a sustained sideslip maneuver will involve a zero yaw rate. Note that a yaw rate is a measurement of rotational velocity while a slip angle is a measurement of relative position.
Consider a momentary yaw rate brought about by rudder deflection with the wings held level. That momentary yaw rate will result in a slip of some angle (which angle will depend on a number of factors including but not limited to amplitude and duration of yaw rate), but to sustain a sideslip will necessarily require a zero yaw rate. That is to say, to fly in a sustained sideslip maneuver—as opposed to a slipping turn—the angular difference between the relative wind and aircraft's longitudinal axis must be maintained with a zero yaw rate.
While yaw rate or angle can be controlled by rudder, there are several other forces or control inputs that can affect or control yaw rate or angle. As one example, consider an asymmetrical thrust scenario involving a sustained sideslip and zero yaw rate. In that scenario, rudder input opposite the direction of the sideslip may be required to maintain the sideslip.

@Jonathan Walters Ok got that there is no specific relation but as you said " ...but to sustain that sideslip will necessarily require a zero yaw rate." How is it true in case of an uncoordinated turn, as it may have a constant yaw rate but still some sideslip angle.

@Swati As a maneuver, a sideslip generally refers to an established slip with sideways movement and no rotation rate about the vertical axis. The terms slip, sideslip, and forward-slip are sometimes used interchangeably and I understand they can be confusing. You seem to be referring to a slipping turn which will involve a slip as well as rotation about the vertical axis.


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How was the endurance test in the Cessna 172 legal?
The flight in the Cessna 172 lasted around 64 days with two pilots switching to fly the plane. To my knowledge both FAA and EASA have rest periods which pilots have to follow. Also the refueling was done by a truck matching the speed and handing over a hose to refuel. How was this flight legal regarding rest periods and refueling maneuver?

A private Part 91 flight like this has different rest requirements for the pilots than do airline pilots.

Plus this was done way before those types of rules existed.

Regarding flight time, duty periods, or rest requirements, no current regulations would have specifically imposed limitations on this flight. This flight would have been operated as a private flight under 14 CFR 91 under today's regulations.
The flight, duty, and rest requirements are specified only for certain commercial operations including airline, charter, and fractional. Flight instruction is also generally limited to 8 hrs in a 24 hr period. Paid pilots routinely fly 12-14+ hours in a day, including in certain patrol activities and in flying private jets.
Refueling is not generally restricted by FAA aiation regulations in a way that would specifically impact this operation. As with the flight time concern, the catch all "careless and reckless" regulation might apply first.
For some of the same reasons that the crew flight time was not restricted, many of the maintenance requirements such as 100 hr inspections, would not be required of a private flight. However, the 100 hr seat rail inspection AD would be problematic today.

The flight you're referring to occurred in 1959.
The Federal Aviation Agency, a precursor to the Federal Aviation Administration, had just been newly established in 1958, and hadn't drafted the rules you're referring to yet.

O tempora, o mores.

As noted in the comments Crew Rest Periods are only applicable to commercial flights operating under part 121, 135 and 91K as per the FAA's regulation, specifically 14 CFR § 121.471. But it does not apply for flights strictly operating under part 91 which they likely were.
You can make a case that they could have potentially been in violation of

14 CFR § 91.13 - Careless or reckless operation.
(a) Aircraft
  operations for the purpose of air navigation. No person may operate an
  aircraft in a careless or reckless manner so as to endanger the life
  or property of another.

but that is the FAA's catch all and somewhat broadly applicable when they see fit. There have been various endurance records set over the years (all legally) and in all cases precautions were taken to ensure that the flight was safe. Generally this involves two pilots taking shifts however the recent Solar Impulse flight set the solo record.
As for the refueling, there is no regulation that an aircraft must be on the ground, or stopped in order to re-fuel, the military refuels mid air quite often.

This is inaccurate. Crew rest periods also apply to §135 and §91K operations.

@JWalters updated to reflect


text:
How many variations are there of the Avro Lancaster?
How many different variations of the Avro Lancaster are there?

There were twenty-three different variants, according to Wikipedia:
British-built variants (13)

Ten combat variants (B.I, B.I Special, B.I (FE), B.II, B.III, B.III Special, B.IV [Lincoln B 1], B.V [Lincoln B 2], B.VI, B.VII)
Two reconnaissance variants (PR.I, GR.3/MR.3)
One SAR variant (ASR.III/ASR.3)

Canadian-built variants (10)

Two combat variants (B.X [later 10S/10U], B.XV [Lincoln XV])
One dual-purpose combat/reconnaissance variant (10BR)
Three dedicated reconnaissance variants (10AR, 10MR/10MP, 10P)
One SAR variant (10S&R)
One trainer variant (10N)
One drone-mothership variant (10DC)
One jet-engine testbed variant (10O)

Plus the Avro Lancastrian, a commercial airliner derived from the Lancaster B.X (the first few Lancastrians were direct conversions of existing B.Xes, although later batches were built as airliners from the start).


text:
Difference between ETA and On-Block time?
I see that the definition of the ETA (Estimated Time of Arrival) according to Eurocontrol is:

(SESAR) the time computed by the FMS for the flight arriving at a point related to the destination airport
(ICAO) For IFR flights, the time at which it is estimated that the aircraft will arrive over that designated point, defined by reference to navigation aids, from which it is intended that an instrument approach procedure will be commenced, or, if no navigation aid is associated with the aerodrome, the time at which the aircraft will arrive over the aerodrome.

For VFR flights, the time at which it is estimated that the aircraft will arrive over the aerodrome.

However I do not understand what is the difference with the Estimated On-Block time.
Would you be able to explain the difference please?

The Eurocontrol Lexicon can help here as well. The Estimated In-Block Time is defined as:

The estimated time that an aircraft will arrive in-block.

(Eurocontrol)
This is not very helpful, but the definition for Actual In-Block Time is:

The actual date and time when the parking brakes have been engaged at the parking position.

(Eurocontrol)
This time is relevant for gate availability because the aircraft is expected to be at its gate (or remote parking position) at this time.
The Estimated Time of Arrival is, as your quote says, a time where the aircraft is still in the air. This is relevant for Air Traffic Control because the number of aircraft that can fly an instrument approach to the destination airport at the same time is limited. If too many aircraft have a similar estimated time of arrival, some will have to hold in a pattern or are delayed on-route already.


text:
Can the ILS be shut down?
Can the ILS be manually turned off? Not by the pilots inside the cockpit by simply shutting of the ILS button, but rather by a 3rd party personnel, such as an ATC or a ground crew member.
ATC shuts off ILS on RWY 05L for safety reasons.. or traffic separation reasons.
I am a second year electronics and communications student, so if you would like to use a couple of technical terms, i can understand them, to some extent

An ILS is powered by electricity, so of course it is possible to shut it off. Your question is unclear.

not asking why, i'm asking how could they be shut down.  A matter of How rather than why.

How? By turning off the power. The same way you could shut down a radio or TV transmitter. If there's no power, there's no transmission.

I'm wondering how exactly you think shutting down ILS would solve traffic separation issues...

The ILS, or precisely the components localizer and glidepath antennas can be shut off, as they are electronic devices that emit radio signals. They can be turned off and on by ATC where required, e.g. having the same ILS frequency for two opposite runways and you only want one to be active at the same time or they can be shut down by maintenance directly at the emitters. ILS are usually not powered by UPS, so they will not be available during power outages.
If equipment is being shut down for maintenance or other reasons, you will see this mentioned in the NOTAM, such as here from Cologne/Bonn Airport, where the glidepath portion of the ILS runway 24 is out of service:
A4932/15 - ILS GP RWY 24 OUT OF SERVICE. 01 OCT 00:00 2015 UNTIL 30 DEC 00:00 2015 ESTIMATED.
CREATED: 27 AUG 13:34 2015

(Source: NOTAM EDDK)

Yes.
Usually, shutting down the ILS means shutting down the localizer and glideslope signals. There is more than one reason to 'shut down' the ILS.
The ILS is designed to shut down automatically on detection of fault. FOr example, if the primary transmitter (of glideslope) malfunctions, the system will automatically transfer to the standby transmitter. If that fails or if the standby transmitter also malfunctions, the system automatically will shut down, with ATC being automatically informed. Cat III ILS systems are required to shut down within 2 seconds of fault detection.
FAA carries out flight check operations on various navigational aids in airports and can require the ATC to shut down the ILS if error is more than limits.
ILS can be shut down because of equipment change, maintenance etc. Of course, if the power goes out, ILS goes out with it.
As per regulations, any shutdown of ILS (or any other navaid) is to be informed via NOTAM.

"if the power goes out, ILS goes out with it": FAA requires a second power source to be used as a backup (I think ICAO as well). Order 8400.13D: "The LOC, glideslope, and inner marker (if operationally required) must have an approved backup power source which provides an uninterrupted power supply in the event of a primary
power source outage.".

@mins True, but Murphy's law applies :) For example, see here

Indeed :) Interesting page and stories, including this one.


text:
How to completely track a plane, not a flight?
This probably has already an answer somewhere, but probably don't know the proper search keys to find the information.
Out of curiosity today I was trying to track a flight: one of my friend texted me about her flight being a lot late, and for fun I wanted to try to see if it was possible to understand what caused the delay. I knew flightradar24 by fame and found too flightaware by chance; I tried with the flight number (EZY2604...if this is the flight number) and couldn't find many information, 'till I realized that EZY2604 is probably something like the callsign for the route plus the scheduling, so with that I can only find details for this combination. And I can only track a plane which is flying, it seems.
TL;DR: how can I go from a flight number to the full route of the physical plane in the previous hours?

Did your friend give you the right flight number? It seems that EZY2604 does not exist. The closest number would be EZY2600.

It exists, but only on FlightAware it seems. But it seems to have another code, U22604. EasyJet list it under both.

It would be EZY42EA in fr24.com then.

I know with United they have a mobile app that includes a "where is this plane coming from" which you can continually click until you find the one that departs late. Most likely the aircraft was delayed on the ground somewhere, so if you are looking for an oddly-long flight you probably won't find it. This is almost always because of a mechanical problem or a crew time-out problem which dominoes from a one-two hour delay to many hours later and eventually the flight being cancelled.

If you want to look for the airplane that flew a certain flight (U22604/EZY42EA for your case), you could go onto flightradar24.com/data and search for that specific flight to find the list of aircraft which flew with the callsign and if you select any one of the planes, you can find out the flight history of that plane for the past few months. You could also search flightaware.com/ for flight history too.

I did a small edit to the question to make it less specific. I want to accept your answer, but could you edit it to be more generic? I think it would be more useful for others :-)

@motoDrizzt Is that better?

EZY is the ICAO airline identifier for EasyJet. U2 is their IATA identifier. That's why it's listed as both. Normally Flight Aware and FlightRadar24 both use the 3-letter ICAO ID. It's a little unusual to have to search with the IATA code, but go figure.
The problem with tracking a plane instead of a flight is that the system doesn't know which aircraft is being used until it actually pushes back. There's always the possibility of a last-minute aircraft change.
SMSvonderTann's method of looking up past flights and seeing what aircraft flew the route before will get you a possible, or maybe even probable tail no. but if the flight is delayed there's a possibility that it is being swapped out.
You can see from the listing that the plane that flew EZY2604 from ATH to MXP flew the reverse EZY2603 from MXP to ATH right before. You can then try looking up 2603 and see what the status is on that.
Problem is you never really know for sure if they might change the aircraft until it's in the air. And a delay makes that more likely.


text:
How are bird strikes tested in helicopters?
Bird strikes are pretty well tested for planes, but what about helicopters?
Do they happen as frequent as planes and if so, what would be the possible outcomes?
Do helicopter emergency procedures include a "bird strike" event?

There are no bird strike standards for helicopters weighing less than 7000lbs in the US. For helicopters over 7000lbs, the windshield must be able to withstand a 2.2lb bird. There are no standards set for rotor strikes as far as I can tell.

Your title and actual question do not really fit together. The title asks if strikes happen to helicopter while the body asks if they are tested for strikes.

Sorry I got carried away with the subject. I'll refactor.

Do they happen as frequent as planes?

Here is a link to the Federal Aviation Administration's Wildlife Strike database. Here you can search all the recorded wildlife strikes in the USA, and filter them by various things, including Engine Type.
To get a good idea of how many helicopter bird strikes occur in comparison to other aircraft, we can compare how many bird strikes occurred in turboshaft (Engine Type F) engine aircraft to the total number of bird strikes.
From January 1, 1990 to January 1, 2017...

California
   - There have been 31 turboshaft engine wildlife strikes, accounting for 0.22% out of the total 13,698.
Texas
   - There have been 46 turboshaft engine wildlife strikes, accounting for 0.30% out of the total 15,520.
Florida
   - There have been 22 turboshaft engine wildlife strikes, accounting for 0.20% out of the total 11,119.

This data would suggest that roughly 0.25% of all wildlife strikes are on helicopters.
Taking another piece of data from the FAA, we find that the ratio of rotocraft to general aviation aircraft in 2015 is 9,766 to 199,927, meaning that helicopters account for roughly 4.66% of total aircraft.

Combining these two pieces of data, we can see that since 0.25% of all wildlife strikes are on helicopters, but helicopters account for 4.66% of aircraft,  helicopters encounter wildlife strikes at a rate of ~18.64 times less than general aviation aircraft.
(Disclaimer: Data used above is rounded and averaged. This is a ROUGH estimate!)

Would you know where to look to find out if any of these strikes ended in a catastrophic failure of the aircraft?

You can also search by civil and military damage, see the Damage (Civil) and Damage (Military) tables at the bottom of the database search page. With the Civil damage, you can filter D for destroyed, then look up the event to see if any casualties were sustained.


text:
What really causes a low-pressure gradient over the top of an aerofoil?
As air flows over the top of an aerofoil the pressure drops. Compared to the high / normal pressures on the underside, a pressure gradient is formed with higher pressure further above the wing. You get:
less pressure = less particles = less density
This sketch summarizes what I know so far:

My questions are:

Does lower air density above the wing mean the air weighs less compared to the weight of the air underneath the wing? If the difference is negligible then it's OK, we can forget it.
What forces act on the air particles causing them to speed up?

Its the shape on top of the wing. Lets refer to newtons law the second that states that if you have a straight line airspeed will not change, but on a jet or airliners wing it is slanted downwards which increases the airflow speed and results Iin a high pressure under the wing and a low pressure above the wing. Think of yyourself going down hill on your bike and you dont have to pedal to get down the hill, it has the same effect as going down a hill on your bike, gravity pushes down on the airflow making it go faster on top and slower on the bottom.

is this right ??so the air particles speed up (due to  gravitys downward pull) as they move arcoss towards the  back of the wing due to the downwards slope of the rear of the wing  as they speed up they are elastically pulled further apart  this then cause less particles per unit vol in a given space and there for less localised pressure

thanks Ethan I think its starting to make more sense now !!

if your question is really of this kind I feel it should be better asked on physics.SE

Pressure is equivalent to static energy. But in lift, the inertial forces on the air molecules play an important part as well. Please read this answer and then let me know if there is still something unclear.

Your welcome. Feel free to ask more questions.

WHAT FORCES ACT ON THE AIR PARTICLE CAUSING IT TO SPEED UP
IS IT GRAVITY PULLING IT DOWN ??
OR IS IT THE CENTRIPITAL FORCE FROM THE CURVED RADIUS SHAPE OF WING ??

to me this is more and more about physics (and shouting won't achieve anything).

I didn't mean to type capitals

here is the question again

as it was meant to be typed originally  it this correct?? the force that acts on the particle causing it to speed up over the top of wing Is as per rotational dynamics  (a centripetal force acting towards the wings curved radius centre

as it was meant to be typed originally question to Ethan it this correct?? the force that acts on the particle causing it to speed up over the top of wing Is as per rotational dynamics  (a centripetal force acting towards the wings curved radius centre  this method would work for sails on yachts that have aerofiols perpendicular to gravity  but still generate lift inorder to move forward

This is my understanding: A combination of the shape, angle of attack and movement of the wing creates high pressure on the front side of the wing and low pressure on the back side. By front and back I mean the part that is facing the oncoming air and the part that cannot "see" the oncoming air.
The low pressure is there because of this. This is the pressure difference which causes lift. Some lift also comes from the downdraft caused by air moving downwards at the trailing edge of the wing due to the angle of attack.
This article has a video that shows airflow over a wing.
http://www.cam.ac.uk/research/news/how-wings-really-work

Uhhh... Newton's Third law requires that all lift exerted by the air on the wing is equal to the down force exerted by the wing on the air


text:
What is this stem on the underside of a Cessna 172R (1997)?
There is a stem that is located on the underside of the airplane between the drain valves for the fuel strainer and reservoir tank. It looks like a small stem that is protruding.
I have noticed it leaks a small amount of fuel (1 drip per 5 seconds). I am going to talk t my instructor about it but wanted to know what it was called. I am not seeing it in the fuel system diagram.

Updates:
I believe it is a part of the electric auxiliary fuel pump, but want any input.
The aircraft is a Cessna 172R made in 1997.
It is 100LL that is dripping.
Here is the fluid dripping.... Not water.

A) have you confirmed that it's fuel leaking? (i.e. it smells like fuel) B) You can edit your own post and include your thoughts, instead of adding them as a comment.

I once noticed it was dripping as we were towing the aircraft during pre-flight, and immediately raised my concern to my instructor. He confirmed it was water, not fuel (it smells and touches different). It rained the night before, so we figured it was just rain water.

What C172 variant? I used to fly a C172P, and I don't remember any auxiliary fuel pump or reservoir tank. It did have a low point drain right under the cabin.

Ok - got word from the local a&p that this stem is a part of the aux fuel pump. It drains the motor side of the pump of any fuel in case the seal that separates the motor from the pump fails. You wouldn't want fuel getting inside of where the motor has current and sparks, hence this "stem" is the safety backup. The entire pump had to be replaced because overhauling made less sense due to the age of the pump. Turns out it wasn't in the diagrams at all!


text:
How can I know if North Atlantic Tracks have been amended?
Information about the North Atlantic Tracks is issued through Track Messages. The NAT Doc 007 document states that every track message is identified by the TMI (Track Message Identifier) number:

The originating OAC identifies each NAT Track Message, within the
Remarks section appended to the end of the NAT Track message, by means
of a 3-digit Track Message Identification (TMI) number equivalent to
the Julian calendar date on which that OTS is effective. For example,
the OTS effective on February 1st will be identified by TMI 032. (The
Julian calendar date is a simple progression of numbered days without
reference to months, with numbering starting from the first day of the
year.).

In case the North Atlantic Tracks are modified, a letter is appended to the TMI number:

If any subsequent NAT Track amendments affecting the entry/exit
points, route of flight (co-ordinates) or flight level allocation are
made, the whole NAT Track Message will be re-issued. The reason for
this amendment will be shown in the Notes and a successive alphabetic
character, i.e. ‘A’, then ‘B’, etc., will be added to the end of the
TMI number (e.g. TMI 032A).

I would like to know how such change is notified to the interested parties; is some ATCs issuing a NOTAM to declare that some changes have been done to the TM? If yes, where can I visualize such NOTAM?
One possible way to overcome my problem would consist in constantly checking if the TMI number has changed but this is not a very efficient way to proceed. I would rather expect some NOTAM which notifies the TMI number change.
Can you tell me if what I ask is plausible? If yes how can I proced?

Related: Where to download NATs (North Atlantic Tracks) information?

The track system may be not updated after the daily issuance (one system at night, the other at daytime), due to the difficulties involved: "To provide a smooth transition between the night-time and the daytime OTS, a period of several hours is allocated between the termination of one system and the commencement of the next. These periods are from 0801 to 1129 UTC and from 1901 to 0059 UTC (source). Possibly the only update could be to fix erroneous data.

For starters I am not completely knowledgeable with the North Atlantic Tracks but work with some of the other Flex track systems in the world. And they are all very similar.
The Track Messages are a type of NOTAM. They are released everyday and revised NOTAM (Track Message) is released if there are changes. They increment the alphabet character on the end of the TMI so that when a clearance is   issued by Air Traffic Control(ATC) they know which track they are flying including the version and ATC can correct it if the pilot has old information.
Extract from one of the Track Message:

REMARKS.

TMI IS 013 AND OPERATORS ARE REMINDED TO INCLUDE THE TMI NUMBER AS
PART OF THE OCEANIC CLEARANCE READ BACK.

When there is any changes they reissue the entire NOTAM (Track Message). So requesting accessing the message again will tell you straight away what is current. Usually aviation doesn't care about what it was, only what it is and what it will be. The computer systems that the airlines use get the most up to date data when they create the Flight Plans.
The question is what you want to do with the data to how the best way to get the data. But the link you supplied will always have the most recent ones.
Visualization of the these tracks, plus others, can be done on SkyVector. Go to layers to change any settings. The link automatically loads up on an ERC High with North American and Pacific Tracks Selected.


text:
Were there any folding wing biplanes?
Given that several nations had operational carriers by 1920 and biplanes were still in military service, were there any folding wing biplanes?

Wikipedia: United States first purpose built aircraft carrier, USS Langley (1920), note no biplanes have wings folded.

Fairey Swordfish, operated off Royal Navy carriers in WW2.  Supermarine Walrus, a single engine pusher flying boat carried on cruisers.  Similar vintage.


text:
How long are modern variants of the F-16 expected to be in production?
The F-16 seems to keep receiving updates and new aircraft appear to still be in production, e.g. the F-16I and F-16Q. It seems there are also several upgrades being developed and installed, such as radar (AESA) and radar detection warning systems.
Has any authority on the subject attempted to estimate how long the F-16 is expected to be in production? Is there any estimated limit on for how long a budget fourth generation airframe can be used as the basis of a modern combat aircraft?
I'm not looking for speculation from StackExchange users but rather a reference to a statement made by one or several external authority -- to avoid making this question opinion based. Some sensible original reasoning is only a bonus as far as I'm concerned.
I can only imagine myself that countries that keep buying F-16s do so for budget reasons -- however, there must also be some real value in buying F-16s in 2019, since these are after all large sums of money even if it is bleak in comparison to e.g. F-35s or F-22s.

If the F-35 gets improved, the F-16 will have a shorter lifetime. But I doubt this will happen much

@Pheric: What's the price tag difference between an F-35 and a modern F-16. I doubt that the market for F-16s will go away soon.

An article last month in the Greenville News about the relocation of the F-16 production line provided this comment:

The Trump administration fast-tracked a $1 billion F-16 deal with
  Bahrain, Navarro said. Deals closed or on the verge of closing since
  then guarantee the plant in Greenville will stay busy at least through
  2025 and likely much longer, he said.

The "likely much longer" will be based on future sales (and Government approval of those sales.) It's a good plane at a competitive price, but a change in the marketplace could mean it ends after this contract build.


text:
Can an F-16 land on an aircraft carrier, at all?
Looking at the F-16 again, I noticed the tailhook which it seems to have. I know the F-16 is not designed to land on any aircraft carrier, however, if it was between ditching in the ocean and attempting to land on a carrier. During wartime or any emergency; if the F-16 found itself over an ocean and needed to land, and there was a friendly carrier nearby. Could it be done?
For this we assume an unmodified F-16, any of the F-16 variants are candidates for this thought experiment. However, I assume the lighter F-16A (I assume they all have the hook, even the early block A variants?) is better, since it has less mass which needs to come to a full stop?
I understand that this will probably be speculation at best, I'm just curious. Forgive me. If someone happens to know the figures of maximum load on the F-16 tail hook versus what would roughly be required, that would be awesome. However, I'm also taking just educated guesses.
My own layman efforts towards an answer, limited to mostly just identifying some obvious issues:
Is the F-16 tail hook even compatible with the arrest system an aircraft carrier uses? Perhaps it wouldn't catch the arrestor cable at all.
If it does catch it, perhaps it is not designed for that kind of abuse, and would tear straight off the airframe if this was attempted.
For carrier landings, the aircraft will typically from what I understand not flare and make hard landings which really beats the undercarriage. I'm not so concerned with the undercarriage breaking, it would be better to recover an F-16 with broken undercarriage than losing it to the ocean.
However, if the undercarriage does break, it might prevent the hook from catching the cable at the correct angle. Even if it does grab the cable, perhaps the aircraft with broken undercarriage would risk sliding off the side of the deck.
From what I understand, there are no barriers on modern Nimitz carriers any longer. Hence they will not be considered as an option. Perhaps a barrier could catch an F-16 but I'm more curious about the properties of the hook, undercarriage, and other issues with landing on a carrier.
I know landing on a carrier is hard, so what is it that makes it so hard for an F-16?

F16 pilots most likely haven't gone through any carrier landing training, which could be the biggest risk. Carrier landing is hard.

Nimitz class carriers still have a barricade.

It can land on a carrier for sure. The question is whether it (or whatever is left of it) will be able to take off.

The plane could, but could the pilot?!

The hook is for emergency use at airports that have Runway Arrestor Systems.  Lots of non-naval fighters have arrestor hooks for that purpose.
Now, there is nothing stopping someone from landing an F-16 or any other fighter on a carrier deck and using its arrestor system, which works the same way.  The main issues are the proficiency required to do it and the ability of the airframe to take it.
A carrier landing isn't really a landing; you more or less descend into the ocean and the deck gets in the way.  So the airplane needs a pilot trained to do that sort of thing, and an airframe that can do it repeatedly, that is, land with a descent rate of >500 fpm, a "hard landing" for a normal airplane, without developing cracks here and there and everywhere after a few dozen times.
No doubt that in theory, you could take a carrier qualified pilot, check him/her out in the F-16, and that pilot could shoot traps onto a deck with the F-16 using the hook (launching it is another matter in the absence of catapult link).  But they wouldn't be able to do a lot of them before the airframe would be toast.

The hook would never hold, it isn't meant for carrier loads. It would end up in the drink anyway.

There is enough fudge factor in the structural design that don't think it would rip off and could probably take a couple of traps.  But yes something would bend or crack pretty quickly.

Not just that, but the landing gear itself isn't designed for the high vs landings typical of carrier operations.

Is the Runway Arrestor System intercompatible with aircraft carrier hook systems? Isn't this the biggest concern when allowing an F-16 to attempt grabbing the cable on a carrier?

No, the F-16 cannot "carrier land", even with the tail hook.
The Air Force jets (aside from any that are shared with the Navy) have tail hooks only for emergency purposes during landing, or securing the aircraft during engine run-up testing. The tail hooks are not designed to arrest an aircraft like it would for a carrier landing, the land-based arresting systems are much gentler on the airframe. The tail hook would get ripped off by the carrier system.
The scenario you present is almost impossible. The jet would have to fly quite some ways out to find a carrier and the carrier would certainly deny landing clearance. They would tell the pilot to eject near the carrier and they would go pluck them out of the water. If ejecting wasn't an option, they would ask them to ditch near the carrier so they could recover them quickly. They could just as easily find a place to land on solid ground for the distance they would have to go.
The issue with landing on the carrier is not just the skill, but all the equipment that is on the deck. If they allowed that to happen, they'd have to clear the deck and the only way to do that quickly is to push the aircraft over the side. As far as I can tell, that has only happened once in history.

Related.  I'm not saying you're wrong but asking a pilot to eject seems like a pretty serious step.  Of course damaging the carrier or harming any of the ship's crew would be serious as well.

Re: last sentence - I have seen WWII videos of crews pushing damaged aircraft off the flight deck. And there is at least one instance of crews pushing possibly good aircraft over the side where they were making room for aircraft of a damaged carrier to land.  [https://en.wikipedia.org/wiki/USS_Franklin_(CV-13)]

They could just as easily find a place to land on solid ground for the distance they would have to go. What if an F-16 was trying to refuel and the refueling failed and now he was running on fumes such that there was a carrier in range but no friendly airfield in range. Actually, I suppose in that case most of the sorties should be run from carrier anyway, but you could have a batch (in a big operation) coming from farther away, counting on refueling coming & going.

@manassehkatz-Moving2Codidact They would ditch near the carrier. Carrier landings, even if possible, take a certain amount of training. They wouldn't risk a full flight deck/people for one aircraft and an untrained pilot (the Navy does not fly F-16's).

OK. That does make sense, assuming the pilot was not already carrier proficient, and I agree that is very unlikely because (except in fiction) pilots don't jump around like that. But I think it gives a reasonable "why was the F-16 even there" possibility.

Do you have any citation for 'the tail hook would get ripped off by the carrier system'? Many structural components (including in aviation) are grossly overengineered for their intended use - see for example, elevators in buildings, which can generally accommodate an order of magnitude more weight than their 'maximum load.'

Yes the F-16 would be able to land on a carrier however it would most likely break/damage the landing gear and other components because it's not built for it. I am only assuming this, but I believe the net as shown in the picture could catch several non-naval aircraft including a F-16.

Could you please add some sources to your answer?

Sorry I don't have any sources as I was told this by my father who used to worked on naval aircraft on the USS. Theodore Roosevelt.

Something not yet mentioned is that the vertical speed typical of carrier operations is way higher than that for typical F-16 (or any non-naval type) landings.
The landing gear of the F-16 is not designed to handle the resulting loads and would be liable to collapse, it's simply not strong enough.
You can see this easily by comparing the landing gear of an F-16 with that of the similar class F/A-18. Notice how flimsy the F-16's legs look in comparison to those of its naval brother? And how the Hornet has far stronger shock absorbers built into its landing gear than does the F-16?
There was an idea to adapt the F-16 to carrier operations at one point, which would have included a stronger landing gear, stronger main fuselage spar, and other modifications for carrier operations, but the Navy decided the resulting aircraft didn't meet their performance specifications (range, payload, etc.) and opted for the F/A-18 instead.
Some links about the plan:
https://en.wikipedia.org/wiki/Vought_Model_1600
https://www.defensemedianetwork.com/stories/v-1600-the-carrier-capable-f-16-that-wasnt/

During wartime or any emergency; if the F-16 found itself over an
  ocean and needed to land, and there was a friendly carrier nearby.
  Could it be done?

I'd say yes, using the barricade, one time in extremis. The pilot would have to fly a really flat pass to not knock off the landing gear, but a really good pilot highly motivated to not die flying a good aircraft on a day with a steady deck could do it. He could a few practice runs at it while burning off the rest of his gas.
I'm not sure the carrier Skipper wouldn't recommend he jump out next to the boat, though.

the airboss would tell him to eject close to the flattop rather than risk fouling up his deck.

You could make the same argument about any barricade event.

Not really. There are cases where ejection isn't possible. Either because there are no ejection seats (think an E-2 or C-2) or where ejection is otherwise no option (say an EA-6 with a seriously injured crewman who'd not survive ejection, or an aircraft with a damaged ejection seat).

The E2 crew could bail out. The F16 could have a fubar ejection seat.  Any barricade event is going to foul the deck for a good bit, no matter what.

A: the emergency hook on an F-16 is not meant for full speed carrier arrested landings. it' is meant to catch an airfield Arrestor wire after a landing and roll down the runway in event of brake failures.  The speed is too high and too violent in a carrier landing and would rip the hook right off.
B: the F-16's landing gear are designed for a smooth flared landing that is typical on a fixed airfield and would collapse under the impact of a carrier landing.  Naval aircraft do not flare their landings and instead basically fly into the deck at speed, and then immediately go to full power in case of a bolter (hook skip).


text:
Time Tracking: Does Turboshaft count towards Turbine time?
another edit
To clarify - I'm programming an application for logbook tracking and want to automate turbine time calculations to help people fill in insurance firms easily.
edit: I guess a more general way to ask this is do you consider turbo shaft to count towards turbine time? Do insurance companies have a standard opinion?
original question:
For insurance forms, when you are asked your turbine time, do you include all of the following in that hour calculation:

Turboprop
Turbojet
Turboshaft

I want to make sure I'm not short changing my time, but don't want to put some helicopter specific turbine in my time if that isn't correct. As far as I'm concerned they should count, right? It is, after all, only asking about the source of thrust not category of aircraft...
Thanks!

I don't want to be unhelpful, but what I or anyone else thinks about this is completely irrelevant. The only opinion that counts is the one from your insurance company.

Turbine is turbine.  If you burn fuel to spin a turbine that drives a compressor, it's turbine.
I counted all turboshaft time as "turbine" when reviewing resumes for pilot applicants.  Understanding the theory behind turbine engine operation is what everyone cares about, whether is was a turbo-this or a turbo-that is not as important.
Contact a few insurance brokers just to be sure.  Falcon Insurance, AOPA, TrueCourse just to name a few.

This confirms my thinking - and gives me some direction as to where to go for more information. Thanks.


text:
When were airbrakes used for the first time in aviation?
I would like to have some information about the history of airbrakes.

Guess that was in first world war. The stukas needed it for their dive.

@NoahKrasser: Stukas? First world war? I think you got your wars confused.

i saw from discovery channel p38 lightning was crashing because it was so fast at diving, no other plane fast like it before, and engineers started to place some sort air spoilers to slow down plane at diving. and i guess no other planes that fast before even when diving because lack of good aerodynamics design induces high drag when diving. this is not answer but i guess it is answering, what is the first necessary airbrake?

by the way discovery channel states, engineers wasnt aware of air behavior over certain speed before.

Airbrakes were probably used on gliders first (for quick landing).

@FredLarson Ah, sure, thanks! Of course second world war! Don't know why I wrote "first".